What is the brain’s mechanism for decision-making? In spite of all we know, this critical cognitive function has yet to be captured by a unifying formalism, akin to E = mc2. This is just becoming possible. In this talk we will introduce a class of single-equation probabilistic procedures that make choices based on sets of simultaneous noisy spike trains, thereby joining neural signalling in its native format with decisions at the behavioural level. We go on to show that, when making choices based on the statistical structure present in the sensory cortex of the monkey, such procedures –ideal Bayesian observers for two alternative settings- render reaction times far shorter than those of monkeys, under the same conditions. This predicts that animals lose some of the information in this structure. By…